This invention relates to a machine for cutting, conditioning and windrowing crop material such as grasses and legumes and more particularly to an improved machine in which a generally transverse rotary disk or drum cutter bar delivers cut material rearwardly to an adjacent impeller rotor, parallel to the cutter bar, for conditioning and discharge into a window.
In machines of the above type, it is typical for adjacent drums or disks to be driven in opposite directions and it is well known that such an arrangement tends to concentrate crop material in the bite between disks or drums so that the rearward discharge from the cutter bar is heavily differentiated with a concentration of material flow corresponding to each pair of disks or drums. When crop material is delivered in this way to a conditioning means which is transversely undifferentiated, the material will be unevenly treated, some receiving too much conditioning and some, where the flow of material is concentrated, receiving too little.
Attempts have been made to deal with this problem as disclosed for example in U.S. Pat. No. 3,673,779, Scarnato, et al, and French Pat. No. 2,121,333. Scarnato discloses mower-conditioners in which a disk or drum cutter bar delivers material to conditioning rolls (rather than an impeller rotor) and in which the disks or drums of the cutter bar are provided with means for throwing material "with horizontal fanning effect" into the rollers to spread the material along the length of the rollers. Although it may be possible in this way to improve distribution along the length of the rollers and hence improve uniformity of conditioning, a disadvantage of this approach is that the "fanning effect" involves a further change of direction of rapidly moving material, consuming additional power in a machine which already has an inherently high specific power consumption.
The French Pat. No. 2,121,333 discloses an impeller mower-conditioner including a rotor having a plurality of tines, the effective length or reach of the tines being increased locally to coincide with the center of concentration of material flowing from the disk or drum cutter bar and it is argued that the resulting larger periphery of the rotor and higher tip speed of the tines in this area offset the concentration of material. But it is well understood that in a machine of this type, for adequate function, the tips of the rotors must pass relatively close to the cutter bar over the whole width of the machine and, therefore, only a limited variation in effective rotor diameter can be tolerated. The drawings of the French patent cited indicate a ratio of maximum to minimum diameter for a rotor used in conjunction with drum cutters of four to three and an even smaller ratio for a rotor used with disk cutters. However, in typical operating conditions, variations of concentration of crop material delivery along the length of the cutter bar with a ratio of at least two to one are encountered, and the variations in rotor diameter suggested by the French patent are insufficient to compensate for such a range of concentrations.
In addition, it is desirable to maintain approximately constant clearance along the length of the rotor between the tips of the rotor tines and the hood over the rotor, particularly in the area where the rotor tines are carrying crop material up and over the rotor. If a straight hood is used with a rotor having a diameter varying along its length, clearance between the rotor tine tips and the hood will vary with adverse effect on material flow. On the other hand, adoption of a hood configuration conforming at least in part to the profile of a rotor having a varying diameter would increase cost of manufacture and could cause additional direction changes in the flow of crop material with a further increase in power consumption as well as possibly adversely affecting windrow formation.